The Bottom of the World is the Antarctica of Hekinoe, a big fat pile of ice and desolation and weather that is potentially far colder than -50 degrees Fahrenheit on a good day. I have designed it to basically copy the climate and environment of Antarctica, with some embellishments. It is cold there, really cold, cold as Hell, and frankly, there isn't that much to do.
I've told the guys that A'lst is there, and his compound is basically the only point of civilization in the cold white expanse. He has a heavily defended compound designed to preserve his people from the elements, and the other dangers of The Bottom of the World while he does his work. If the weather isn't quite enough, there are a few other dangers as well. The Bottom of the World has its own version of the great ursines from The Beast Lands, bigger and angrier bears as white as the snow around them.
So to derail for a minute, dire has always been DnD's word for big faux-prehistoric animals. They base it on reality, then put big bony spurs on it. The dire bear is actually called a cave bear, and to give you an idea on size, the biggest of grizzly bears are about the same size as the smallest cave bears. Modern polar bears are about the size of cave bears, though the range of their sizes extends to both smaller and larger than the cave bear. None of this is relevant really, my great ursines are still ridiculously big, just like all the beasts of The Beast Lands. The great white ursines are bigger than the great ursines, so that is special.
Additionally, like many continents in Hekinoe, The Bottom of the World has its own variety of giants living in its icy bosom. Unlike The Known World, these giants are aggressive and violent, huge blue-skinned creatures that are tusked and craft crude axes out of razor sharp ice. Sometimes they gather in tribes, sheltering in the shadow of big black stone pyramids, others just wander the icy wastes hunting for food. They usually just wear the thick hides of dead great white ursines as armor, as they are incredibly resilient to the deadly cold of The Bottom of the World.
Beneath the thick ice of The Bottom of the World, are huge black pyramids, not tiered city things like Meroteth, but actual black pyramids. They're not glassy like Meroteth and the Necropolis either, more like black granite or something along those lines, and they're not the black stone of Kethranmeer's hammer and Steeltown's walls. (A side note, it occurs to me that perhaps there are too many types of black stone in Hekinoe.) Just big, silent, black pyramids beneath the ice. A'lst has played around with and explored them a little, but they're not his main purpose for wandering south.
So, in short, The Bottom of the World is a dangerous place. The cold will kill you, the natives will kill you, and the critters will kill you. So what is it that A'lst seeks there? Peace and quiet in which to work, certainly. Whatever other reasons he may have will be up to the players to discover.
So I guess there is some info and mystery, and hopefully stuff that will interest the players, despite the general emptiness of the place.